water simulation -Move water upward along a slope
In the Scene settings, switch off Gravity by unticking the checkbox. This will enable the Gravity settings in the Fluid Domain Settings. You can then adjust the gravity such that the 'uphill' becomes 'downhill' and the water naturally flows uphill.
Note that this depends on the topology being such that the water will naturally flow in the desired direction - eg, up an indented riverbed. If the situation is more complicated you may need to resort to other methods to 'Guide' the water along the path but this would risk making the motion less natural.